1. Field of the Invention
This invention relates to the preparation of substituted ethylene epoxides.
2. Discussion of Prior Art
Substituted ethylene epoxides such as propylene oxide and butylene oxide, etc. are well known in the art as monomers used in the preparations of resins of various types ranging from epoxy adhesive application to elastomeric solvent resistant polymers for use in making tubing, shoe soles and the like. These epoxides are also useful in the preparation of polyols for use in polyurethane foams. These substituted ethylene epoxides can be prepared by the direct oxidation of an olefin or by treatment of the corresponding halohydrin with lime. These processes have yet to be perfected and the direct oxidation routes are especially difficult due to the formation of a variety of by-products which render the processes uneconomical.
It is disclosed in U.S. Pat. No. 4,069,234 that substituted ethylene carbonates may be converted to substituted ethylene epoxides using various catalysts including tin(II) carboxylates. Stannous acetate is specifically mentioned.
In accordance with the present invention, it has been discovered that substituted ethylene epoxides may be prepared from substituted ethylene carbonates by catalytic conversion using catalysts containing at least one carbon-tin bond wherein the tin is tin(IV). These compounds are generally known as organo-metallic compounds specifically organo-tin compounds. It is recognized in the art that the tin compounds containing carbon-tins bonds are a separate and distinct class of compounds from the tin(II) compounds of the U.S. Pat. No. 4,069,234 mentioned above. For example, in the publication, Organo Metallic Compounds, volume 2, Springer-Verlag, New York, Inc. 1967 at the preface at page V it is stated:
"The aim of this compilation has been to provide a comprehensive, non-critical source of information concerning organic-metallic compounds. The scope is limited to the compounds containing at least one carbon-metal bond."
Thus, the present invention discloses that substituted ethylene carbonates may be converted into substituted ethylene epoxides using new catalysts heretofore not disclosed by the prior art.